Eye surgery is now commonplace with some patients pursuing it as an elective procedure to avoid using contact lenses or glasses to correct myopia, hyperopia, and astigmatism, and others pursuing it to correct adverse conditions such as cataracts. Moreover, with recent developments in laser technology, laser surgery is becoming the technique of choice for ophthalmic procedures. Indeed, some surgeons prefer a surgical laser beam over manual tools like microkeratomes and forceps, because the laser beam can be focused precisely on extremely small amounts of ocular tissue, thereby enhancing accuracy and reliability of the procedure.
Typically, different laser eye surgical systems use different types of laser beams for the various procedures and indications. These include, for instance, ultraviolet lasers, infrared lasers, and near-infrared, ultra-short pulsed lasers.
For example, in the commonly-known LASIK (Laser Assisted In Situ Keratomileusis) procedure, an ultra-short pulsed laser is used to cut a corneal flap to expose the corneal stroma for photoablation with ultraviolet beams from an excimer laser. Ultra-short pulsed lasers emit radiation with pulse durations as short as 10 femtoseconds and as long as 3 nanoseconds, and a wavelength between 300 nm and 3000 nm.
Besides cutting corneal flaps, surgeons use ultra-short pulsed lasers to perform cataract-related procedures, including creating cataract entry incisions, capsulotomies, as well as fragmenting and softening the cataractous lens prior to enable easier removal. They also use them to create relaxing incisions in the cornea to correct a patient's astigmatism. Examples of laser systems that provide ultra-short pulsed laser beams include the Abbott Medical Optics iFS Advanced Femtosecond Laser, the IntraLase FS Laser, and the Catalys Precision Laser System.
The ability to produce an angled side cut is a highly desired feature in ultra-short pulsed surgical systems used for cutting corneal flaps. This is because the angled side cut enables proper repositioning of the corneal flap after the corneal bed has been ablated with the excimer laser's ultraviolet beams. Proper repositioning of the flap in turn improves the flap edge's regrowth and healing.
Known methods for creating an angled side cut, such as those used in the Abbott Medical Optics iFS system and other conventional ultra-short pulsed laser systems, involve X-Y galvanometers (or “galvos”) scanning the laser focus to produce a series of rings of different diameters while the Z-scanner of the system moves slowly vertically. While these methods are suitable for lasers with pulse repetition rates (commonly referred to as “rep-rate”) in the hundred KHz range and beam delivery optics covering the entire field of view for corneal flap cutting, they are not optimum for other ophthalmic surgical laser designs that do not meet these characteristics.
Hence, improved systems and methods are needed for making an angled side cut for corneal flap creation during laser ophthalmic surgery.